Little CMS wrapper for Rust

Convert and apply color profiles with a safe abstraction layer for the LCMS library.

See API reference for Rust functions and the LCMS2 documentation HTML/PDF for more background information about the functions.

```rust use lcms2::*;

fn example() -> Result<(), std::io::Error> { let iccfile = includebytes!("customprofile.icc"); // You can use Profile::newfile("path"), too let customprofile = Profile::newicc(icc_file)?;

let srgb_profile = Profile::new_srgb();

let t = Transform::new(&custom_profile, PixelFormat::RGB_8, &srgb_profile, PixelFormat::RGB_8, Intent::Perceptual);

// Pixel struct must have layout compatible with PixelFormat specified in new()
let source_pixels: &[rgb::RGB<u8>] = …;
t.transform_pixels(source_pixels, destination_pixels);

// If input and output pixel formats are the same, you can overwrite them instead of copying
t.transform_in_place(source_and_dest_pixels);

Ok(())

} ```

To apply an ICC profile from a JPEG:

rust if b"ICC_PROFILE\0" == &app2_marker_data[0..12] { let icc = &app2_marker_data[14..]; // Lazy assumption that the profile is smaller than 64KB let profile = Profile::new_icc(icc)?; let t = Transform::new(&profile, PixelFormat::RGB_8, &Profile::new_srgb(), PixelFormat::RGB_8, Intent::Perceptual); t.transform_in_place(&mut rgb); }

There's more in the examples directory.

This crate requires Rust 1.64 or later. It's up to date with LCMS 2.15, and should work with a wide range of versions.

Threads

In LCMS all functions are in 2 flavors: global and *THR() functions. In this crate this is represented by having functions with GlobalContext and ThreadContext. Create profiles, transforms, etc. using *_context() constructors to give them their private context, which makes them sendable between threads (i.e. they're Send).

By default Transform does not implement Sync, because LCMS2 has a thread-unsafe cache in the transform. You can set Flags::NO_CACHE to make it safe (this is checked at compile time).

Upgrading from v5

If you're using a custom RGB type with Transform, implement bytemuck::Pod and Zeroable for it. Make sure you use arrays or #[repr(C)] struct types for pixels. Rust tuples have a technically undefined layout, and can't be used as as a pixel format.

unsafe impl Pod for RGB {} unsafe impl Zeroable for RGB {}

You don't need to do this if you use the rgb crate.